Contact lenses are widely used around the world to correct many of the most common visual defects, such as myopia, hypermetropia or astigmatism.
Contact lenses of the multifocal type, in which the dioptric power of the lens varies according to the distance from the optical axis of the lens, are also known.
This type of lens is typically used for the correction of visual defects that affect short-distance and long-distance vision, providing zones with differentiated dioptric powers according to graduations that may assume quite complex profiles.
An example of a multifocal contact lens of the type described above is known from U.S. Pat. No. 6,322,213 in the name of Euro Lens.
However, contact lenses of this type are complicated to produce, and furthermore the results obtained in terms of ability to correct visual defects are not always satisfactory.
Consequently, there is still a need in the relevant technical field to produce a contact lens capable of allowing both effective long-distance vision, particularly in the presence of ametropic defects such as hypermetropia and myopia, possibly combined with astigmatism, and effective short-distance vision, particularly in the presence of defects arising from loss of accommodation in the crystalline lens of the eye, such as presbyopia.
US 2010/0265458 discloses a contact lens, specifically designed for the treatment of diplopia, in which a central region is rendered optically inactive by darkening or by significantly increasing the dioptric power, so as to create a scotoma that essentially occludes the entire region of the fovea of one of the two eyes. In order to achieve this aim, US 2010/0265458 states that the optically inactive region must have a diameter of between 1 mm and 6 mm.
Indeed, this lens produces a substantial shadow cone on the retina that is perceptible to the user, so that if this lens were used on both eyes, the user's vision would be compromised.